Secondary Gravity Waves From the Tonga Volcano Eruption: Observation and Modeling Over New Zealand and Australia

• Published in: Journal of geophysical research. Space physics 2023-10, Vol.128 (10), p.n/a
• Main Authors: Figueiredo, C. A. O. B., Vadas, S. L., Becker, E., Wrasse, C. M., Takahashi, H., Nyassor, P. K., Barros, D.
• Format: Article
• Language: English
• Subjects: atmospheric models; Gravity waves; Ionospheric effects; Ionospheric electron content; ionospheric models; Phase velocity; Ray tracing; Tonga eruption; Traveling ionospheric disturbances; Updraft; Volcanic activity; Volcanic eruptions; Volcanoes
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2023JA031476

The biggest volcanic eruption since 1991 happened on 15 January 2022 on the island of Hunga Tonga‐Hunga Haʻapai (20.6°S; 175.4°W) in the South Pacific between 4:00 and 4:16 UT. The updrafts from the eruption reached 58 km height. In order to observe its ionospheric effects, approximately 750 GNSS receivers in New Zealand and Australia were used to calculate the detrended total electron content (dTEC). Traveling ionospheric disturbances (TIDs) were observed over New Zealand 1.0–1.5 hr after the volcano eruption, with a horizontal wavelength (λH ${\lambda }_{H}$) of 1,525 km, horizontal phase velocity (CH ${C}_{H}$) of 635 m/s, period (τ) of 40 min, and azimuth (α) of 214°. On the other hand, TIDs were observed 2–3 hr after the eruption in Australia with λH ${\lambda }_{H}$, CH ${C}_{H}$, τ, and α of 922 km, 375 m/s, 41 min, and 266°, respectively. Using reverse ray tracing, we found that these GWs originated at z > 100 km at a location ∼500 km south of Tonga, in agreement with model results for the location of a large amplitude body force created from the breaking of primary GWs from the eruption. Thus, we found that these fast GWs were secondary, not primary GWs from the Tonga eruption. Key Points The first TIDs observed over New Zealand and Australia originate at z > 160 and z > 100 km about 436 km southeast of the eruption This location agrees with model results for the body force created by the dissipation of primary GWs from the eruption The first TIDs observed over New Zealand and Australia are secondary, not primary, gravity waves from the eruption